Promotion and Demotion

At the end of each tournament all players sharing first place are promoted to the next higher tournament class. All players sharing last place are demoted to the next lower class.

The example shows the final results of a ficticious 7 player tournament. After the last game of this tournament the players Alpha and Beta would be promoted and the players Epsilon, Theta and Eta would be demoted. Only the players Gamma and Delta would remain in the same tournament class.

Promotion - but to which class?

At first sight, this seems to be a stupid question.

"If you win a tournament of class B, you are promoted to class A"

This sounds logical, but is it really that simple?

What if the player won another tournament of class B shortly before and has been promoted to class A. Will he now be promoted to class E?

Or if he lost that other B tournament and has been demoted to class C. Will he be promoted to class B or to class A, now?

More extreme cases can be imagined (and have happened already!). Since players are allowed to play several tournaments in parallel, it is possible that a player may play tournaments in two or even more different classes. One must distinguish between two different terms:

The class of a player (PC)

This is the highest tournament class a player may currently enroll in.

The class of the tournament (TC)

Every tournament is of a certain class. Only players of that class may enroll in that tournament. During the course of that tournament one or the other of the players may be promoted or demoted to a different class (by winning or losing other tournaments). But this doesn't change the tournaments' class, of course. The class of a tournament is a static attribute, it doesn't change.

All players participating in a tournament of class N had the same player class N
when they enrolled to that tournament. While the player classes might change over the life time of the tournament, the tournament class remains unchanged.

Solution

With these definitions in mind, the solution of those ambiguities is relatively simple.

TC

What happens?

New PC

PC+2

win => promotion

PC+1

PC+1

win => promotion

PC+1

PC

win => promotion lose => demotion

PC+1 PC-1

PC-1

lose => demotion

PC-1

PC-2

lose => demotion

PC-1

New player class

The class of a player (PC) changes by one step at most.

Promotion

A player is promoted after winning a tournament of class TC if his player class PC is equal or lower than the tournament class.

Demotion

A player is demoted after losing a tournament of class TC if his player class PC is equal or higher than the tournament class.

Examples

A player of class B wins a tournament of class B. This is the simple case: PC = TC = B, he is promoted to class A.

A player of class B wins a tournament of class A. Here is PC = B and TC = A. Since PC < TC, he is promoted to class A (again).

A player of class E wins a tournament of class A. Here is PC = E and TC = A. Since PC > TC, he is not promoted.

A player of class E loses a tournament of class A. Here is PC = E and TC = A. Since PC > TC, he is demoted to class A.

A player of class E loses a tournament of class B. This is an improbable case. The player would be demoted to class A.